A life of a rolling bearing varies due to a variety of complexly intertwined factors such as a material, a form, a size, a lubricant state, and a load of a bearing ring or a rolling element of the rolling bearing. Accordingly, in order to obtain the rolling bearing which has an appropriate durability according to a use, it is necessary to perform a testing in order to know effects which the various factors exert on the life of the rolling bearing. FIG. 7 illustrates a radial rolling-bearing testing device in an example of the related art (for example, refer to Patent Document 1). In the radial rolling-bearing testing device, a leading end section (the left end section in FIG. 7) and a portion near to a base end of a rotary shaft 2 are rotatably supported inside a fixed housing 1 by a pair of radial rolling bearings 3 and 3 which each are bearings to be tested. A movable housing 4 is disposed concentrically to the rotary shaft 2 in a periphery of a center section of the rotary shaft 2 which is positioned between the radial rolling bearings 3 and 3. The movable housing 4 is provided inside the fixed housing 1 in a state in which a displacement in the radial direction is possible and a displacement in a rotation direction is prevented. Then, a support bearing 5 is provided between an inner peripheral surface of the movable housing 4 and an outer peripheral surface at the center section of the rotary shaft 2. Then, lower half sections of the support bearing 5 and the radial rolling bearings 3 and 3 are immersed in lubricant which is retained in a lubricant reservoir 6 that is provided inside the fixed housing 1. According to the need, foreign matters 7 and 7 such as metal powders and ceramic powders are mixed into the lubricant. A radial load F with a desired value which faces a vertical direction (up-and-down direction in FIG. 7) is freely applied to the movable housing 4 by a pressurizing device such as a hydraulic cylinder.
In a case where a life testing of the radial rolling bearings 3 and 3 is performed, the radial rolling bearings 3 and 3 are pressed in the vertical direction via the movable housing 4, the support bearing 5, and the rotary shaft 2 by pressing the movable housing 4 using the pressurizing device, and the rotary shaft 2 is driven so as to rotate. As a result, the life testing for durability evaluation of the radial rolling bearings 3 and 3 can be performed in a state in which the desired radial load F is applied and rotated at the desired rotation speed.
In a case where the life testing of the radial rolling bearings 3 and 3 is performed using the radial rolling-bearing testing device as described above, vibration values (amplitudes) of the radial rolling bearings 3 and 3 are detected by a vibration sensor, and a point in time, when the vibration values exceed a threshold value that is set in advance, is set as the life of the radial rolling bearings 3 and 3. And then the testing is completed. However, when the vibration sensor is directly attached to the radial rolling bearings 3 and 3 which are bearings to be tested, it requires work to reattach the vibration sensor every time the radial rolling bearings 3 and 3 are replaced, which is troublesome. Therefore, it is considered that the vibration sensor can be attached to any of the rotary shaft 2, the support bearing 5, and the movable housing 4 which are vibrated in synchronism with the radial rolling bearings 3 and 3. However, in a case where the vibration sensor is attached to any of the rotary shaft 2, the support bearing 5, and the movable housing 4, there is a possibility that splashes of the lubricant which is retained inside the lubricant reservoir 6 splatter on the vibration sensor, and a portion of any of the rotary shaft 2, the support bearing 5, and the movable housing 4 in which the vibration sensor is installed comes to be a high temperature due to heat which is generated by a heater for maintaining an oil temperature of the lubricant at an appropriate temperature. As a result, there is a possibility that errors in the value which is detected by the vibration sensor increase, and the vibration sensor breaks down.